This invention relates to a vehicular rearview assembly. More particularly, the present invention relates to mounting of a rain sensor within a rearview mirror assembly support.
Rain sensors for detecting moisture due to rain, road splash, and the like on the outside of a vehicular windshield are conventionally mounted to the inner cabin surface of the vehicle windshield. Rain sensors typically comprise a light emitting diode, an array of light emitting diodes which are paired with a photo detector, or an array photo detectors. The rain sensor may detect moisture by sensing a change in the amount of light refracted at the outer windshield surface due to the presence or absence of moisture or use other techniques such as sending backscattering of light caused by raindrops.
Various mounting methods have been proposed with a common method including optically coupling the rain sensor detector usually to the inner cabin surface of the vehicle windshield. Rain sensor detectors are conventionally coupled to the inner cabin surface by use of an optical adhesive, or by using a removable mount, for example a mount of a type disclosed in U.S. Pat. 4,871,917 to O'Farrell assigned to Donnelly Corporation of Holland, Mich., the disclosure of which is incorporated by reference herein. In removable mount constructions, such as are disclosed in the Donnelly '917 Patent, the rain sensor detection surface, which typically comprises a resilient optically clear polymer material, such as a silicone material, is mechanically pressed between the detector and the inner windshield surface by the mount.
Thus far, conventionally known means for mounting rain sensor units to vehicle windshields have several disadvantages. Optical adhesives are difficult and expensive to remove during service replacement of a damaged windshield. Furthermore, the optical adhesives, which are used to attach the rain sensors to the inner surface of the windshield, may be visible from the outside of the vehicle and, thus, can potentially detract from the vehicle appearance and styling. Moreover, the attachment of the rain sensor to the windshield either by bonding with an adhesive or by mechanical attachment often creates a noticeable obstruction of the forward field of view due to the separate and, frequently, bulky housing provided for the rain sensor unit. Furthermore, the location and bulky size of the rain sensor unit may further increase the risk of potential injury of the vehicle occupants should they impact the windshield in an accident.
In general practice, the windshield manufacturer often attaches a mirror mounting button to the windshield, for example a mounting button of the type disclosed in U.S. Pat. No. 4,930,742 assigned to Donnelly Corporation, which provides a releasable mount for the rearview mirror assembly to the windshield, the disclosure of which is incorporated in its entirety herein. When these mounting buttons are attached to the windshield, the manufacturer may need to attach a second structure, such as a mechanical guide or rail to which the rain sensor is then later attached to the vehicle, which would ultimately increase the cost of the windshield.
More recently, rain sensors have been mounted within the support arm of the interior rearview mirror assembly. These constructions utilize the teaching of the Donnelly '917 patent as follows. Referring to FIGS. 7-9, this prior art interior rearview mirror assembly 300 includes a mirror housing 302 which supports a reflective element 304 and which is mounted to the windshield W by a support arm 306. Support arm 306 is coupled to housing 302 by a ball and socket connection 307. The rain sensor 308 is mounted inside support arm 306 and positioned to view the outside surface of windshield W. Support arm 306 includes a biasing member 309 and is adapted to releasably engage a mirror mounting button 310, which is attached to the inner surface W′ of the windshield W and typically installed by the window manufacturer for coupling rearview mirror assembly 300 to the windshield (FIG. 9). In this system, mirror mounting button 310 is a ring shaped member 312 with a hollow center 314, which is glued to the inner surface of the vehicle windshield. Support arm 306 engages the outer rim of mirror mounting button 310 when the mirror assembly 300 is attached to button 310 during assembly of the vehicle at the vehicle assembly plant or during service. The rain sensor is located within the cavity of the support arm approximate the mirror mounting button and is biased into contact with the glass surface through hollow center 314 by biasing member 309. Support arm 306, however, only provides a single point of articulation for housing 302, since it must remain in a fixed position at the juncture of the support arm and the windshield in order to maintain the alignment of the sensor with the mounting button.
Although the aforementioned construction has several advantages, it has numerous disadvantages that can limit its widespread application in vehicles. By locating the rain sensor within the support arm, the support arm must necessarily include a cavity that is large enough to accommodate the rain sensor unit. Furthermore, this construction requires that the articulation of the mirror housing about the support arm be limited to a single point at the juncture of the support arm to the housing. As mentioned above, the juncture of the support arm to the mounting button must remain fixed so that rain sensor maintains contact with the inner surface of the windshield. Therefore, the present design is limited for use on single pivot mirror supports and is unsuitable for dual pivot mounting supports, which are commonly used on a wide variety of vehicles. It is also necessary to stock a special mirror design when a rain sensor is desired, which adds to inventory requirements.
Referring to U.S. Pat. Nos. 4,936,533 and 5,100,095 both assigned to Donnelly Corporation, the disclosures of which are incorporated by reference in their entireties, dual pivot mounting supports typically include a double ball joint which comprises an outer tubular support arm member with sockets formed at both ends. The sockets receive ball joints extending from the housing and mirror mounts to provide a greater range of movement for the rearview mirror assembly. Positioned in the cavity of the tubular member is a helical spring which retains the respective ball joints in the ends of the tubular support arm. Therefore, double ball joint mirrors would appear to not be well suited to accommodate a rain sensor unit within the support arm cavity.
Other considerations include vibration performance. The presence of the rain sensor in the support arm increases the weight of the rearview mirror assembly. With increased weight, potential exists for detrimental effects on the mirror assembly vibration performance. Furthermore, placement of the rain sensor in the support arm limits the choice of rearview mirror suppliers since only a limited number of mirror assembly support arm designs can accommodate such mounting of the rain sensor. Additionally, most countries have regulations that require mirror assemblies to break away upon impact in an accident. With the design illustrated in FIGS. 7-9, the choice of the mirror button design is, therefore, also limited, thus placing potential limitation on the use of these rain sensor mounts in certain countries.
Consequently, there is a need for an improved rain sensor mount for a vehicle that overcomes the above disadvantages and achieves its purpose in a manner that is economical and convenient for the automaker. Furthermore the improved rain sensor mount preferably provides broad application by allowing flexibility in the choice of design. Moreover, the improved rain sensor preferably is consistent with current safety goals and enhances the performance of the interior rearview mirror assembly.